C#

泛型参数是不变的，c# 4.0为泛型类型引入了协方差和逆变性 可覆盖的类成员必须显式地标记为virtual

Java

缺少无符号数字数据类型 基本数据类型不是对象

c# / .net:

Classes should be sealed by default There should be no lock statement - instead, you should have specific locking objects, and there should be methods such as Acquire which return disposable lock tokens. Corollary: there shouldn't be a monitor for every object. GetHashCode() and Equals() shouldn't be in System.Object - not everything's suitable for hashing. Instead, have an IdentityComparer which does the same thing, and keep the IComparer<T>, IComparable<T>, IEqualityComparer<T> and IEquatable<T> interfaces for custom comparisons. Poor support for immutability Poor way of discovering extension methods - it should be a much more conscious decision than just the fact that I'm using a namespace.

这些都是我想出来的，明天问我，我会想出一个不同的5个:)

C#

当被枚举的集合中的对象发生变化时，foreach命令弹出， UI控件吐出假人，因为它们在错误的线程上访问。当然是所有的调度员。调用可以移动到CLR管道， PInvoke，编组等， 我浪费了两年时间学习远程遥控， 它没有露比性感。

我讨厌所有语言的五件事(至少就我所知):

Does what I say/type, not what I mean Will undoubtedly meet people who think they are experts in the language, but just make a mess of it (e.g. people who insist that removing comments/unused local variables will speed up execution time for a program) Unless the language is obsolete, then it will probably continue to evolve (either the actual language, or the concepts behind using it effectively) requiring you to actively develop with it so as to not fall behind. Can't modify the lexer/compiler (add in own context sensitive grammar) No perfect language (every language is missing some sort of useful feature that usually is either impossible to simulate, will unavoidable have an ugly interface or just require far too much time to implement and get it right)

ActionScript / AS3

没有抽象类 没有私有构造函数(所以单例是一种hack) FP10之前没有类型化数组 Flash IDE中的编译/发布时间慢得离谱 内置函数(例如Math)的性能较慢

除此之外，它实际上是一种很好的语言——与流行的观点相反，它比JavaScript好得多，比PHP之类的语言好一百万倍。

C#

它是一种很棒的语言，特别是在LINQ中，但是与c++相比泛型支持较差。它有如此多的潜力，但目前的实现只对强类型集合和类似的琐碎事情有用。下面举几个例子:

A generic argument cannot be restricted to enums (only classes or structs). A generic argument cannot be a static class. Why? This seems like a completely artifical restriction. You cannot specify that a generic type must have a constructor with a certain signature because you cannot have constructors on interfaces. Why not? It's just another method with the special name ".ctor". Similarly, you cannot specify that a generic type must have a static method, because those also cannot be declared on interface. Something like static T Parse(string s) would often come in useful. The compiler is too eager in prohibiting some casts which the programmer knows would actually work, so they require uglyness like (TheRealType)(object)value No covariance, eg. IList<string> cannot be converted to IList<object>, even though string[] can be converted to object[]. (Microsoft might be fixing this in C# 4.0, though.)